Gastric cancer is known to be the first or second largest cause to cancer-related death worldwide. Further, gastric cancer is one of the most common cancers, with a high incidence rate. According to the Cancer Facts & Figures reported by the Korean National Cancer Center, gastric cancer accounts for 15.4% of the total cancer cases of South Korea in 2009, ranking second for the entire population and first in men.
Gastric cancer exhibits various symptoms ranging from none at all to severe pain. Further, gastric cancer may cause only nonspecific symptoms, that is, symptoms that are specific not only to gastric cancer, but also to general digestive disorders. On the whole, gastric cancer produces no noticeable symptoms in its early stages. Even though present, the most common symptom of early gastric cancer is felt as light dyspepsia or epigastric discomfort by patients who are thus apt to regard it as insignificant, which contributes to the increased mortality of gastric cancer.
To date, the screening for and detection of gastric cancer resorts, for the most part, to physical means. First, gastric X-ray examination may be performed using a double contrast agent, with gastric compression, or on mucous membranes. Alternatively, gastroscopic examination may be the diagnostic method of choice. It allows the inside of the stomach to be visualized so as to detect those lesions which are too small for X-ray-based detection. Further, a questionable lesion can be biopsied via gastroscopy, thus increasing the diagnostic yield of gastric cancer. However, this physical examination is disadvantageous in terms of hygiene and in that the patient under examination suffers potential discomfort or pain. In recent years, active research has been directed toward the diagnosis of gastric cancer by measuring expression levels of gene markers specific for gastric cancers.